(SPACE.com) -- NASA is reviewing over two dozen proposals to extend the useful scientific life of the Hubble Space Telescope, as well as safely dispose of the Earth orbiting observatory at the end of its life in space.

There is growing support for robotic servicing of the Hubble, but whether or not augmenting the telescope with new astronomical gear utilizing robot hardware is possible remains uncertain.

NASA's Goddard Space Flight Center in Greenbelt, Maryland is now reviewing ideas from a variety of groups, including universities and major aerospace firms. According to NASA, Goddard has received 27 proposals ranging from a few pages to one tome of 200 pages length from a leading aerospace firm.

The proposals are in response to a Goddard "Request for Information" on Hubble Space Telescope End of Mission Alternatives in February, with the NASA center receiving the proposals March 22. At present, a review of submitted ideas and discussions with proposal groups is actively underway.

NASA said that the request resulted in ideas mostly from industry, but did include views from other government agencies, academia, as well as two private citizens. A spokesman said that the ideas are now being evaluated.

However, while the submittals are now being reviewed, any go-ahead on a robotic servicing scheme for Hubble is far from assured.

Robotic exploration

At the core of extending Hubble operations is just how robust methods and technologies are at this point to carry out a robotic servicing mission. Such firms as Lockheed Martin and Ball Aerospace are among teams scoping out how best to extend the life of Hubble.

According to one aerospace executive, the robotic servicing of Hubble fits in well with NASA's Moon, Mars, and beyond plans to push for wider use and adoption of robots to explore beyond Earth's orbit.

At Goddard, an internal panel of experts is assessing the feasibility of robotically changing out Hubble astronomical instruments. Also, an attachable package of batteries and gyroscopes that can be mounted on Hubble, via robotic servicing, is being considered.

Lightning rod decisions

The look at how best to extend Hubble's useful scientific life has been spurred by a NASA decision to cancel a June 2006 servicing mission by astronauts to the space-based telescope. Furthermore, the observatory's retrieval by a space shuttle at the end of its mission is no longer an option, according to the space agency.

In making those judgments, NASA administrator Sean O'Keefe has become a lightning rod for both political and public criticism. NASA policy requires the safe disposal of the Hubble Space Telescope. It is now headed for an uncontrolled reentry into Earth's atmosphere no earlier than the year 2013.

At present, Hubble's projected battery life is the principal limiting factor for overall observatory lifetime

Dump or boost?

NASA's plan is to maximize the telescope's scientific productivity through the remainder of the mission by extending its useful productive lifetime and sustaining its unique capabilities as long as possible.

Once the Hubble science program is no longer viable, the plan is to either dump the facility in a controlled manner into the ocean or boost the observatory to a safe parking orbit over 1,550 miles (2,500 kilometers) above the Earth. To do so requires use of an unproven propulsion module that would be attached to Hubble.

In this scenario, the propulsion stage would be lofted on an expendable launch vehicle. It would then rendezvous, capture, and dock with the telescope. Once those actions are complete, it can be nudged into a controlled reentry or boosted to the higher safe parking orbit.

According to a Goddard document, there may be advantages to performing the deorbit or orbit boost immediately after the completion of science operations, which could be as early as 2007 or 2008.